This invention relates to improvements in tension clamps.
In our Australian Patent Specification No. 463,958, there is disclosed a tension clamp which comprises, in combination, a main jaw co-extensive with an elongated adjusting arm, a movable jaw co-extensive with a hollow housing through which said adjusting arm is adapted to pass freely, an adjustable tension lever pivotally attached to and between two side cheeks of said housing, a secondary lever pivotally fastened at one end thereof to said tension lever by a swivel pin adapted for adjustable location within a travelling slot formed in said tension lever, the other end of said secondary lever being constrained with respect to said housing by means of an eccentric cam set in sliding relationship with respect to a further pair of registering travelling slots, each formed within a respective one of said side cheeks of said housing, said cam being adapted to engage selectively one of a number of semi-circular notches formed within an edge of said adjusting arm remote from said main jaw, an operating handle being provided upon said cam and protruding to the exterior of said housing, whereby a sliding motion of said adjusting arm within said housing is permitted following an arcuate adjustment of said handle in one sense and prevented by the locking of said cam in one or other of said notches following an arcuate movement of said handle in the opposite sense, and whereby a rotary movement of said tension lever with respect to said housing causes the latter then to lock securely with respect to said adjusting arm by an overcenter action to grip firmly within said jaws any workpiece located therebetween.
In use of such a tension clamp, however, it has been found that the necessity to often manipulate both the workpiece to be clamped, and the clamp itself, which in many industrial applications may be quite large and heavy, makes simplification of the operation of the clamp desirable. In particular, in use of the clamp disclosed in Australian Patent Specification No. 463958, it is not only necessary for the operator to adjust the position of the housing relative to the adjusting arm so as to roughly position the jaws of the clamp about the workpiece and to pivotally move the tension lever with respect to the housing, but in addition the operator must operate the operating handle provided on the eccentric cam and protruding to the exterior of the housing when the jaws of the clamp have been roughly positioned.